Semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices that in the past comprised only mechanical components now have electronic parts that require semiconductor devices, for example.
Semiconductor devices typically include several layers of insulating, conductive and semiconductive materials that are patterned to form integrated circuits. There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip. Semiconductor technology has seen a trend towards miniaturization, to meet the demands of product size reduction, improved device performance, and reduced power requirements in the end applications that semiconductors are used in, for example.
Semiconductor devices are typically subjected to many tests throughout the manufacturing process to ensure that their performance meets the device requirements, before shipping them to the end customer. Some tests may be extreme, in order to weed out devices with early life failures. Tests in the industry include wafer sort, wafer acceptance test (WAT), and burn-in tests (BIT), for example. In a wafer sort, intact wafers are tested to determine which of their die are functional. Those that fail the test are marked with a drop of ink and are eventually discarded. In some applications, additional tests are required to ensure operation of the devices at high temperatures and extreme conditions (e.g., in automotive, military, or space applications).
One method of performing the tests on semiconductor devices is by using external circuits in test equipment to tests the integrated circuits. The tests may be performed by contacting the leads of the device after packaging, e.g., by plugging the packaged integrated circuits into specially designed burn-in and test sockets, or by making electrical contact to probe points, contact pads, or bond pads of the semiconductor devices before and/or after die singulation from the wafer and before or after packaging, as examples.
Some recent semiconductor device designs include on-chip test circuits that are used to perform tests. These on-chip test circuits may be used exclusively or in conjunction with external test circuits to perform a variety of tests on the semiconductor devices before either shipping to an end customer, and/or before packaging the devices, for example.
A problem with on-chip test circuits is that because they are connected to the power supply of the functional circuits on the chip, and because they include transistors and other electronic components that have leakage current when connected to a power source, they cause increased leakage current of the semiconductor device even when the on-chip test circuits are not in use, thus resulting in increased power consumption for the semiconductor device.
What is needed in the art is a method of forming an on-chip test circuit that does not increase the leakage current of semiconductor devices, and a structure thereof.